Since the network services became an important part of daily life, the worldwide manufacturers of the network devices put all their attention to build a faster and stable network environment. Users generally divide the network into two different formats; one is wired network environment, and another is wireless network environment. In the field of the wired network environment, for example the Ethernet which is supported by huge numbers of network products, there are many well-defined products for public, so users can build up a reliable wired network environment with little efforts. However, the twisted network cables always bother users, and it looks uncomfortable for everyone. The introduction of the wireless network environment solves the bothering problems, and the wireless technologies grow in a tremendous progress.
Just like the concepts in wired network, the wireless network is built under similar topology of the Ethernet, and many manufacturers start to follow up some industrial standards of WLAN, for example IEEE 802.11, WMAN and IEEE802.16. It becomes so easy for general users to build a wireless network environment in their homes, but the solution is hardly to meet the necessaries in enterprises' and outdoor hotspot's environments. The basic design of the wireless device is like the hub in Ethernet, and this means when the total throughput of the wireless device is over certain amount, and the performance of the wireless network will reduce largely. Because the traditional wireless device, for example Access Point (AP), is designed to be a wireless hub instead of a wireless switch. Formerly engineer only needed to redesign the internal circuit of wired hub, and the overall performance of the hub can be highly improved. In this manner, the hub was eventually replaced by the switch, and it is all about the performance. However, in the field of the wireless network, reaching the solution is a great challenge. Because of the outside factors in the wireless network environment, the characteristic of traditional “input/output (I/O) line” is difficult to be substituted. In wired network environment, the I/O line is coaxial wire, and the performance of the wired network can be improved by skimpily upgrading the quality of the coaxial wire.
In wireless network environment, improvement of the network I/O quality can not be done by this simple method. Because the network I/O is carried by radio frequency (RF,) so the quality of network I/O is highly dependent from antenna design. Plurality of sectored linear (planar) arrays with equal number of the Rotman lens may used as a solution; either dead or overlapped annoying zones within sector crossover regions can be found. It is urgent to have some modular antenna units and corresponding transmission devices in order to implement wireless switch.